<span>First, your endocrine system releases a chemical called adrenaline into
your bloodstream. Adrenaline gives you a burst of energy and prepares
your body to take action. Oxygen is carried by the circulatory system, so
your heart beats even faster to move more blood to your muscles. Your
breath comes faster and faster, too, so that more oxygen can get into
your body. Your body is experiencing stress.</span>
